Elevator systems



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ELEVATOR SYSTEMS Filed Oct. l, 1958 6 Sheets-Sheet 5 BIZCRZ Fig.3.

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20 Claims. (Cl. 187-29) This invention relates to an elevator system having plural operating modes and it has particular relation to banks of elevator cars having operating modes which are automatically selected to provide service best suited for varying tratlic patterns.

Although aspects of the invention are suitable for elevator systems consisting of a single elevator car, the invention is particularly suitable for banks of elevator cars. For this reason, the invention will be discussed largely with reference to a bank of elevator cars.

The traiiic demand variations or the different traflic patterns encountered by an elevator system may be served'by different types or modes of operation, each designed to cope with a specific trailic demand variation or pattern. An elevator system may be transferred from one mode of operation to another mode of operation automatically.

-For example, during most of a business day a demand for elevator service which is predominantly equal in the two directions of travel is generally encountered. For such a traiic pattern the elevator system may be conditioned to provide substantially balancedservice in the two directions.

During certain periods of the day, however, a substantial demand for elevator service in the down direction may be registered. The elevator system may then be transferred automatically to a mode of operation termed down peak operation, wherein service in the down direction is expedited. When conditioned for down peak operation the elevator system may expedite service in a down direct-ion in any suitable manner. Thus, during down peak operation the floors may be divided into a low Zone group and a high zone group. Certain of the elevator cars, termed low zone elevator cars are assigned to provide special elevator service for the low zone of iioors; and the remainder of the elevator cars, termed high zone elevator cars, are assigned to provide special service for the high zone of floors. Such operation is more fully described in the Santini et al. Patent 2,740,495.

It sometimes` occurs, however, that heavy demand for down service is unbalanced; e.g., such demand may exist for a lower `group of floors served by the elevator system While demand for service in the upper group of floors is relatively light. Under these conditions, the division of the bank of elevator cars into two groups, one serving an upper zone and the other a lower zone of floors, might not be justified. If the demand for down service were confined to the lower group of floors, high call reversal circuits Vwould keep the elevator cars in the lower Zone and themost eiiicient service would result; i.e., each of the elevator cars could be conditioned, when traveling up, to reverse at the farthest floor in the low zone for which a call is registered which may be answered by such elevator car. If there is only one down call in the upper group of floors, however, all of the cars or a predetermined number thereof would be required to travel into the upper zone in response to such call. Traffic at the lower iioors then would tend to accumulate, resulting in long waits by prospective passengers, because of the time consumed in making a long run up for the single call and subsequently the long ru"n down to respond to the calls for the floors in the lower group.

In accordance with the invention an elevator system is arranged to provide a irst mode of service. However, under certain conditions the elevator system automatically is transferred or converted to a second mode or a specialized service. In a bank of elevator cars, all of the elevator cars are transferred to the second mode of operation. Such transfer may depend on a factor such as the service demand. In a preferred embodiment of the invention, the service demand is measured by the number of floor calls registered for landings or iioors above the rst or lower terminal oor by prospective passengers.

As an example of a suitable first mode of operation the elevator cars may be arranged to operate between terminal landings or floors in order to provide service not only for the terminal floors but for a pluality of landings or floors located intermediate the terminal floors. Should a large number of down landing calls be registered in a low zone of oors combined with the registration of relatively few landing calls in the high zone of tloors, the elevator cars would require substantial time to answer the calls in the high Zone before responding to the calls registered by passengers desiring down service in the low zone. Under these circumstances, all of the elevator cars may be transferred for operation in accordance with the second mode.

As illustrative of the `second mode of operation, the elevator cars when transferred thereto may be conditioned to serve only the low zone of landings or iioors. In order Vto improve further the eiiiciency of the service in the low Zone, all of the elevator cars may be conditioned, when traveling yup, to reverse at the farthest call for service in the low zone in the direction of the upper terminal landing.

Since the aforesaid unbalanced heavy demand for down service in most instances is likely to exist for only a relatively short period of time, it follows that the second mode of operation provides expedited service for a large number of passengers desiring elevator service from 'the lower group of landings without unduly penalizing other demands for elevator service.

Conveniently, during operation in the second mode, all of the elevator cars may answer car calls registered for landings or floors in both the high and the low zones desired by passengers entering the elevator cars. In addition, the elevator cars may answer calls for up service registered by passengers waiting at the various floors for elevator service in the low zone. Furthermore, the cars, in addition to being prevented from answering the relatively few oor calls for down service in the high zone, may also be prevented from answering calls for up service in such zone. It should be noted, however, that, since transfer to the second mode of operation occurs during a heavy demand for down service in the low zone in conjunction with relatively light demand `for service from the high zone, in most instances during operation in the second mode there will be relatively few car calls and up iioor calls for service throughout the system.

Desirably, the elevator system may be prevented from being reset for the first mode of operation upon the termination of the heavy demand for down service in the low zone as long as certain system conditions exist. In a preferred embodiment of the invention, these conditions are the presence of at least one elevator car in the high zone of floors and a light demand for elevator service from the high zone. When all of the elevator cars which are in the high zone at the termination of the heavy demand for down service in the low Zone subsquently move to the low zone, or when the demand for service from the high zone becomes relatively heavy, the elevator system is reset for the first mode of operation.

It is,- therefore, a first object of the invention to provide an improved elevator system having various modes of operation which are selected automatically in accordance with service demand.

It is a second object of the invention to provide an elevator system as defined in the preceding paragraph, wherein the transfer of the system from a first to a second mode of operation is dependent upon the registration of a predetermined demand for elevator service in a predetermined direction of travel of the elevator cars.

It is a third object of the invention to` provide an elevator system as defined in either of the preceding two paragraphs, wherein the transfer from a first to a second mode of operation is dependent upon the combination of the registration of greater than a iirst predetermined number of calls for service from a first group of landings in a predetermined direction and less than a second predetermined number of calls for service from a second group of landings.

It is a fourth object of the invention to provide an elevator system as defined in the preceding object, wherein upon the occurrence of the predetermined service demand specialized service is provided for the first group of landings.

It is a fifth object of the invention to provide an elevator system having a plurality of elevator cars for serving a plurality of landings, wherein upon the occurrence of a predetermined service demand all of the elevator cars are conditioned to provide specialized service for the same part only of the landings.

It is a sixth object of the invention to provide an elevator system as defined in the preceding paragraph, wherein each of the elevator cars when providing specialized service is conditioned to reverse at the farthest call for service in a first direction of car travel in that part of the landings for which specialized service is provided.

lt is a seventh object of the invention to provide an elevator system as defined in any of the preceding objects, wherein an elevator car assigned to provide specialized service or to provide service in accordance with the second mode of operation upon the occurrence of a predetermined service demand is prevented from being reset to provide service in accordance with the first mode of operation upon the termination of the predetermined service demand except upon the occurrence of a predetermined traffic condition.

Other objects of the invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which:

Figure l is a schematic view with circuits shown in straight-line form f a portion of an elevator system embodying the invention;

Fig. 2 is a schematic view with circuits shown in straight-line form of a further portion of the elevator system illustrated in Fig. l;

Fig. 3 is a schematic view with circuits shown in straight-line form of a further portion of the elevator system' illustrated in Figs. 1 and 2; and

Figs. 1A, 2A and 3A, respectively, are'key representations of relays and switches illustrated in Figs. l, Z and 3. If Figs. 1A, 2A and 3A are horizontally aligned respectively with Figs. l, 2 and 3, it will be found that corresponding contacts and coils of relays andswitches shown in the horizontally-aligned figures are substantially in horizontal alignment.

In order to facilitate the orderly presentation of the invention, a number of conventions has been adopted. Although the invention may be incorporated in an elevator system having any desired number of elevator cars serving a structure having any desired number of floors or landings, it will be assumed that the invention is incorporated in an elevator system having two elevator cars serving a structure having twelve oors or landings. The elevator cars are designated by the reference characters and B.

Because of the similarity of the circuits and components associated with the two elevator cars, components associated with the elevator car B will be identified by the same reference characters employed for the components associated with the elevator car A preceded by the letter B. For example, the resistors R1 and BRI are associated respectively with the elevator cars A and B.

Relays and switches employed for the elevator system may have front or make contacts and back or break contacts. Front or make contacts of a relay are closed when the relay is energized and picked up. The contacts are open when the relay is deenergized and dropped out. Back or break contacts of a relay are closed when the relay is deenergized and dropped out. The back or break contacts are open when the relay is energized and picked up.

Each set of contacts of a relay or switch is designated by the reference characters employed for the relay or switch followed by a suitable numeral specific to the set of contacts. For example, the reference characters U1 and U3 designate the first and third sets of contacts respectively associated with the up switch U of the elevator car A.

In order to facilitate further the presentation of the invention, certain apparatus specific to car A and certain apparatus common to all of the elevator cars are set forth as follows:

Apparatus common to all cars IUR through 1f1U`R---up iioor call registering relays 2DR through HDR-'down floor call registering relays QH-hgh zone quota relay QL-Llow' zone quota relay Figure 1 Fig. l shows thel elevator cars A and B and certain control circuits' associated therewith. The elevator car A' will be assumed to be stopped at the second floor, whereas the elevator car B will be assumed to be stopped at the eleventh iioor of the structure. The circuits and mechanisms associated with the two elevator cars are similar' and will' be understood by reference to those associated with the elevator car A.

The elevator car A is connected by a steel hoist cable 1t) to a counter'w'eight 11. The cable 10 passes over a sheave 12, which is Secured t0 a shaft 13 for rotation therewith. The shaft 13 is rotated by a motor 14 which may be of any conventional type. For present purposes it will be assumed that the motor 14 is a direct current motor having its armature 14A secured to the shaft 13 and having a field winding 14F which is permanently connected across two direct current buses L1 and L2 which supply direct current energy for the control circuits.

The elevator car A has therein a plurality of normallyopen car-call push buttons 1c through 12e which are actuated for the purpose of registering calls respectively for the first to twelfth oors as desired by passengers entering the elevator car.

To permit registration of calls for service by prospective passengers located at the various floors served by the elevator cars, push button stations are located at such floors. Such a station is shown in Fig. 1 for the third floor. It includes a normally-open up floor call push button 3U which is pressed by a prospective passenger desiring elevator service in the up direction. A similar push button is located at each floor from which service in the up direction may be desired. The station also includes a normally-open push button 3D which is pressed by a prospective passenger desiring elevator service in the down direction. A similar push button is located at each floor from which elevator service in the down direction may be desired. The numeral of the reference characters (as 3D or 3U) indicates the floor at which the push button is located.

The elevator car A also has mounted thereon a slowdown inductor relay E and a stopping inductor F which may be of conventional construction. The slowdown relay E has two sets of break contacts E1 and E2 associated therewith. The relay has a normally incomplete magnetic circuit and energization of the winding of the relay alone does not alect the associated contacts. However, if the slowdown relay E reaches an inductor plate UEP located in the hoistway of the elevator car while the winding of the relay is energized, the magnetic circuit of the relay is completed and the contacts` E1 open. In Fig. l the inductor plate UEP is assumed to be mounted in the hoistway to be reached by the slowdown relay E as the elevator car A nears the third floor. If the elevator car A is to stop at the third floor, the winding of the relay E is energized and when the relay reaches the inductor plate UEP for the third door, the contacts E1 open to initiate a slowdown operation for the elevator car. It will be understood that a similar inductor plate is 4similarly associated with each of the floors at which the elevator car A may stop during up travel thereof.

During down travel of the elevator car A, the inductor relay E cooperates with down inductor plates DEP to initiate a slowdown of the elevator car as it approaches a floor at which the elevator car is intended to stop. For example, if the elevator car is to stop during` down travel at the third oor, the winding of the inductor relay E is energized as the elevator car nears the third floor. When the inductor relay reaches the down inductor plate DEP for the third oor, the contacts E2 open to initiate a slowdown operation of the elevator car. It will be understood that a similar inductor plate DEP is provided for each of the floors at which the elevator car A is to stop during down travel thereof.

The stopping relay F similarly cooperates with inductor plates UFP and DFP for the purpose of bringing the elevator car to a stop as it reaches a floor at which it is to stop. Thus, if the elevator car A during up travel is to stop at the third Hoor, the winding of the stopping relay F is energized and as the relay reaches the stopping inductor plate UFP for the third door, the contacts F1 open. These contacts in opening result in stopping of the elevator car at the third floor. A similar inductor plate is provided at each of the oors CII 6 for which the elevator car A is to stop during up travel thereof.

If the elevator car A is to stop at the third floor during down travel thereof, the winding of the stopping relay is energized and as the relay reaches the inductor plate DFP for the third floor, the contacts F2 open to produce a stopping operation of the elevator car at the third oor. It will be understood that a similar inductor plate is provided for each of the floors at which the elevator car A is to stop during down travel thereof.

Because of the large number of control circuits required, itis conventional practice to provide each elevator car with a oor selector 16. This selector includes a plurality of rows of contact segments mounted on the insulating panel 16A. Only two rows of contact segments al through a12, d1 through :112 are illustrated in Fig. l. These contact segments are successively engaged during travel of the elevator car respectively by brushes aa and dd for the purpose of controlling the energizations of certain circuits. For example, if the elevator car A during down travel is to stop at the third floor in response to a car call, the brush aa engages the contact a3 shortly before the elevator car A reaches the third floor, to initiate a stopping operation thereof.

The brushes aa and da are mounted on a brush carriage 16C which is mounted for movement in accordance with movement of the elevator car, but at a greatly reduced rate. In the embodiment of Fig. l, it is assumed that the carriage 16C is in threaded engagement with a screw 16S which is coupled to the shaft 13 through suitable gearing for rotation in accordance with movement of the elevator A. Consequently, as the elevator car A moves, the brushes mounted on the carriage 16C permit the energization of appropriate circuits at various points of travel of the elevator car.

Although the driving motor 14 may be energized in various ways, it will be assumed that the control of this motor is of the type commonly referred to as a variable voltage control. In such a control, a direct current generator 17 has its armature 17A connected in a loop with the armature 14A of the motor. A series field winding 17S for the generator also may be included in this loop. The generator has a main eld winding 17F which is connected for energization from the buses L1 and L2 through a reversing switch. This reversing switch includes contacts U2 and U3 of an up switch. When these contacts are closed, the eld winding is energized with proper polarity for up travel of the elevator car. On the other hand, when contacts D2 and D3 of a down switch are closed, the field winding is energized with proper polarity for down travel of the elevator car. The energization of the field windings is completed through a resistor R1 for slow speed operation of the elevator car or through make contacts VI of a speed relay for full speed operation of the elevator car.

The elevator car A is provided .with a conventional spring-applied electromagnetically-released brake. This brake includes a brake drum 18D which is secured to the shaft 13 for rotation therewith. A brake shoe 18C normally is biased against the brake drum by means of a spring (not shown). The brake is released upon energization of a brake coil 18B which cooperates with a magnetic armature 18A secured to the shoe 18C. The coil 18B is connected to the buses L1 and L2 for energization either through make contacts U1 or through make contacts D1 of the up switch U or the down switch D.

The speed relay V is connected for energization from the buses L1 and L2 through either of two paths. One of these paths includes make contacts U4 of the up switch, a limit switch 19 and the break contacts E1 of the slowdown relay. The limit switch 19 is a carnoperated normally-closed switch which is opened as the elevator car nears its upper limit of travel.

The remaining path of energization comprises make contacts D4 of the down switch, a limit switch 20 and vdown preference relay X- is deenergized).

the break contact E2 of the slowdown relay. The limit switch Ztl may be cam operated. lt is normally closed and is opened as the elevator car A nears its lower limit of travel. p

As long as the elevator car A is running, the running relay M is energized. This relay can be energized only as long as the make contacts DRT of a door relay DR are closed. These contacts are closed only as long as all of the hoistway doors and car doors for the car A are closed. Such safety provisions are well known in the art.

The running relay M initially can be energized only if the break contacts 'MT1 are closed to indicate that sufcient time has elapsed since the last stop of elevator car A to permit discharge or entry of passengers.

Assuming that the foregoing contacts associated with the running relay M are closed, the relay may be energized initially' through either of two paths. @ne of these paths is as follows:

L1, 70Tll, l/Vl, Fl, 2l, U, M, DRl, L2

Since the up switch U is energized through this path, it follows that the elevator car will be conditioned for up travel. The limit switch 2li is a normally-closed rnechanicallyoperated switch which is opened as the elevator car A nears its upper limit of travel. When energized, the up switch U closes its make contacts U5 to establish a holding circuit around the contacts 7Tll and W1.

The second path for initially energizing the running relay M may be traced as follows:

L1, NTL Xlr, FZ, 22, D. M, DRI, L2

Since the down switch D now is energized, it follows that the elevator car A is conditioned for down travel. The limit switch 22 is a mechanically-operated normallyclosed switch which is opened as the elevator car A nears its lower limit of travel. When it picks up, the down switch D closes its make contacts D5 to establish a holding circuit around the contacts 7GT1 and X1.

The slowdown relay E, the inductor relay F, and a holding relay G are energized in parallel from the buses Ll and L2 through make contacts M1 of the running relay M. To complete an energizing circuit for these relays E, F and G, one of three conditions must be present, First, the make contacts T are closed to indicate that a car call is registered for a floor which the elevator car A is approaching. Second, the contacts HC1 are closed to indicate that the elevator car A has reached the farthest registered call in the up direction of travel of the elevator car. Third, the make contacts Sl are closed to indicate that the elevator car A is conditioned to stop at a oor in answer to a registered floor call for such floor.

When the holding relay G is energized, it closes its make contacts G1 to establish with the make contact Mi a holding circuit for the inductor relays E and F.

The direction of travel of the elevator car A is determined initially by an up preference relay W and a down preference relay X. For the up preference relay W to be energized, the break contacts X2 must be closed (i.e., the The limit switch 23 also must be closed. This switch is normally closed and is opened as the elevator car A reaches its upper limit of travel, in this case, the twelfth iloor.

Energization of the up reference relay W also requires closure of at least one of two sets of contacts. These include the break contacts HG2 which are closed as long as a call exists for a floor above the position of the elevator car A. Make contacts MZ are closed as long as the elevator car A is running.

The down preference relay X is energized if the break contacts WZ are closed (i.e., the up preference relay is dropped out) and the limit switch 24 is closed. This limit switch is normally closed and is opened as the elevator car A reaches the lower terminal floor. K

lf the farthest registered call in the up direction of travel of the elevator car A is an up floor call, and if the car has stopped in response to such call, both the contacts HG2 and M2 will be open. ln order to permit the passenger who has registered this up floor call to register a car call for a floor above before the elevator car A becomes conditioned for down travel (i.e., before thedown preference relay X picks up) the up reference relay W has a time delay in dropout of the order of two seconds. When such car call is registered before the relay W drops out, the break contacts HG2 reclose to maintain the relay W picked up, and the elevator car will thereafter proceed to the floor above for which the car call has been registered.

As long as the elevator car A is running, the make contacts M3 are closed to energize the non-interference relay 79T. When the elevator car A stops, the contacts M3 open to de'energize the relay. However, the relay 70T has a substantial delay in dropout. This delay may be provided in any suitable manner, as by connecting a resistor across the relay coil. The time delay in dropout is selected to be suflicient to permit discharge of passengers from the elevator car A or entry of passengers into the elevator car A after each stop.

It will be recalled that the door relay DR is connected across the buses L1 and L2 through contacts operated by each door associated with the elevator car A. If any of the doors are open, the contacts associated therewith are also open to prevent energization of the door relay DR.

Figure 2 Figure 2 shows the call registration circuits for the elevator cars. Car call registration circuits are illustrated for the elevator ears A and B in the upper part of this ligure.

it will he recalled that the elevator car A is provided with a plurality of push buttons 1c through 12C for the purpose of registering car calls. Each of these push buttons has associated therewith a car call registering relay TCR through MCR respectively. The push buttons and call registration relays cooperate with four rows of contact segments located on the iloor selector for the elevator car A. The contact segments a1 through al1 cooperate with the brush aa for the purpose of initiating a stopping operation of the elevator car during down travel of the elevator car respectively at the rst through eleventh floors. The contact segments b2 through blZ cooperate with a brush bb for the purpose of initiating a stopping operation of the elevator car during up travel of the elevator car respectively at the second through twelfth floors. A brush cc cooperates with a row of contact segments c2 through cl2 and a brush dd cooperates with a row of contact segments d1 through dll for the purpose of cancelling registered car calls as they are answered respectively during down travel and up travel of the elevator car. lt will be understood that for each contact segment the numeral of the reference character designates the oor with which the contact segment is associated. Thus, the reference character a1 designates the contact segment for the first floor in the a row.

By reference to Fig. 2, it will be observed that when the car call push button 2c is pressed the car call registering relay ZCI?. is connected therethrough across the buses Ll and L2. This relay closes its make contacts ZCRI to establish a holding circuit around the push button. The contact segments a2 and b2 are connected throughy this set of contacts to the bus L1.

If the elevator car A is set for down travel, the make contacts X3 are closed. Consequently, as the elevator car nears the second floor, the brush an engages the contact segment a2 to complete the following circuit for the car call stopping relay T:

9 t L1, ZCRI, a2, aa, X3, T, L2

The energization of the relay T initiates a stopping operation of the elevator car A at the second floor.

As the elevator car A continues its approach toward the second floor, the contact segment c2 is engaged by the brush cc. As the elevator ,car comes to a stop, the break contacts M4 of the running relay close to complete the following cancelling circuit:

Ll, ZCRl, ZCRN, c2, cc, X4, M4, L2

The operating coil of the registering relay ZCR and the cancelling coil ZCRN are wound in opposition on a common core. Consequently, energization of the cancelling coil ZCRN cancels the effect of the operating coil and resets the registering relay ZCR. Preferably, as the elevator car stops at the second floor, the brush aa passes slightly below the associated contact segment a2; however, the brush cc remains in engagement with the associated contact segment c2 as long as the elevator car A remains at the floor.

Next, it will be assumed that the same call is registered for the second floor as the elevator car A travels up towards the second floor. Under these circumstances, the make contacts W3 and W4 of the up preference relay are closed. As the elevator car A nears the second floor, the brush bb engages the contact segment b2 to complete the following circuit:

L1, ZCRI, b2, bb, W3, T, L2

The energization of the car call stopping relay T results in the initiation of a stopping operation for the second floor.

As the elevator car A continues to approach the second floor, the brush dd engages the contact segment d2 to complete the following circuit:

L1, 2CR1, ZCRN, d2, dd, W4, M4, L2

The energization of the cancelling coil ZCRN resets the call registering relay ZCR. During the stopping operation, the brush bb preferably passes slightly above the associated contact segment b2, whereas the brush dd remains in engagement with the associated contact segment d2 as long as the elevator car A is at the second floor.

The car call registering circuits for all of the intermediate floors are similar to those described for the second floor. For this reason and to conserve space, the intermediate floor circuits are illustrated in Fig. 2 only for the second and eleventh floors.

The car call registering circuits for the upper terminal (twelfth Hoor) may be similar to those employed for the intermediate floors. However, since the elevator car A stops at the twelfth floor only during up travel, contact segments for the twelfth floor need not be provided in the a and d rows. By reference to Fig. 2 it will be noted that only contact segments b12 and cl2 are provided for the twelfth floor.

The car call registering circuits for the lower terminal or first floor may be similar to those provided for the intermediate floors. Since the elevator car stops at the first floor only during down travel, contact segments for the first floor need not be provided in the b and c rows. For this reason, in the car call registering circuits only contact segments a1 and d1 are illustrated for the first floor.

The central part of Fig. 2 illustrates up floor call registering circuits. These circuits are operated by means of normally-open push buttons 1U through 11U which are located respectively at the first through eleventh floors. The push buttons have associated therewith up floor call registering relays lUR through 11UR and cancelling coils lURN through 11URN in a manner which will be clear from the discussion of the call registering relays and cancelling coils associated with the car call push buttons.

rl`he up oor call registering relays 1UR through 11UR and their cancelling coils are associated with contact 10 segments for each of the elevator cars in the bank. For example, a row of contact segments e1 through e12 is provided for the elevator car A and cooperate with a brush ee. A brush ff cooperates with a row of contact segments f1 through 711 for the elevator car A.

Let it be assumed that while the elevator car A is tr-aveling up a prospective passenger waiting on the second floor presses the up floor call push button 2U to energize the up oor call registering relay ZUR. This relay closes its make contact 2UR1 to establish a holding circuit around the push button.

Since the elevator car is :assumed to be traveling up, the make contacts W5 of the up preference relay W are closed, As the elevator car A nears the second floor, the brush ee engages the contact segment e2 to complete the following circuit:

L1, 2UR1, e2, ee, W5, S, L2

The energization of the oor call stopping relay S initiates the stop at the second floor. In response to movement of the car towards the second floor, the brush ff engages its contact segment f2. As the elevator car stops, the break contacts M5 close to complete the following cancelling circuit:

L1, 2UR1, ZURN, f2, ff, W6, M5, L2

This resets the up floor car registering relay ZUR. As the elevator car A cornes to a stop, the brush ee preferably passes slightly above the contact segment e2. However, the brush ff remains in engagement with the contact segment f2 as long as the elevator car A remains at the second floor. By inspection of Fig. 2, it will be observed that the contact segment e2 is connected to the corresponding contact segment BeZ for the elevator car B. Similarly, the contact segment f2 is connected to the corresponding contact segment BfZ for the elevator car B. Consequently, operation of the push button ZU is effective to stop the first uptraveling elevator car which reaches the second floor and which is conditioned to accept the call at the second oor.

The up floor call registering circuits for all of the intermediate iloors are similar. Consequently, such circuits are illustrated in Fig. 2 only for the second and eleventh floors.

During up travel, the elevator cars always stop at the twelfth Hoor if they reach such floor. For this reason, a single contact segment e12 suffices for the twelfth floor and is permanently connected to the bus L1. Since the elevator car A does not stop during up travel at the lower terminal or first floor, a contact segment in the e row is not required. With this exception, the up floor call registering circuits for the first floor are similar to those described for the second floor.

The lower part of Fig. 2. illustrates the down floor call registering circuits for the elevator cars. Down floor calls are registered by operation of normally-open push buttons 2D through 12D which have lassociated therewith down floor call registering relays 2DR through 12DR and cancelling coils ZDRN through 12DRN. Each push button cooperates with its call registering relay and its cancelling coil in the manner discussed with reference to the up floor call push buttons.

For the elevator car A, a row of contact segments g1 through g11 cooperates -with 'a brush gg and a row of contact segments h2 through k12 cooperates with a brush hh. Let it be assumed that the elevator car A while traveling down is approaching the second floor, at which a down floor call has been registered yby operation of the push button 2D. Such operation results in energization of the down floor call registering relay 2DR to close the make contacts 2DR1. Since the elevator car is traveling down, make contacts X5 and X6 are closed.

As the elevator car A nears the second floor, the brush gg engages the contact segment g2 to complete the following circuit:

L1, 2DR-1, g2, gg, X5, S, L2

The energization of the floor call stopping relayl S initiates a stopping operation of the elevator car A at the second hoor'. As the elevator car continues its approach, the brush hh engages the contact segment h2. The stopping of the elevator car A results in closure of the break contacts M to complete the following cancelling circuit:

L1', 2DR1, ZDRN, h2, hh, X6, MS,- L2 The energization of the cancelling coil `resets the call registering relay ZDR. Preferably, as the elevator car A comes to a stop, the brush gg passes slightly below the associated contact segment g2, but the brush hh remains in engagement with the associated contact segment h2.

The contact segment g2 is connectedto the corresponding contact segment BgZ of the elevator car B. Similarly, the contact segment h2 is connected to the corresponding contact segment BhZ for the elevator car B. Consequently, the first elevator car to approach the second floor while traveling down will answer a call registered by the call registering relay 2DR.-

The down oor call registering circuits for all of the intermediate oors are similar. Consequently, such eircuits are illustrated in Fig. 2 only for the second, third, tenth and eleventh floors. The down floor call registering relays for the upper terminal or twelfth hoor also may be similar. However, since the elevator car A does not stop at the twelfth floor during down travel, the contact segment in the g row may be omitted for the twelfth door. Since the elevator car A always stops when it reaches the lower terminal floor, a single contact segment g1 may be provided for the elevator car A, and this contact `segment may be permanently connected to the bus L1.

Figure 3 The upper part of Fig. 3 illustrates high call reversal circuits for the elevator cars. Thus, the elevator car A has a high call reversal circuit 30 which energizes the high call reversal relay HC as the' elevator car A during up travelv nears the highest oor for which a call is registered.

The high call reversal circuit 30 includes in series break contacts for all of the up hoor call registering relays above the first hoor and fo'r all of the down floor call registering relays and all of the elevator car A car call registering relays above the second floor arranged in the order of the floors. The series connection of these contacts may be traced as follows:

To conserve space, high call reversal circuit contacts for the third through the sixth oors are omitted in Fig. 3. The high call reversal relay HC is connected through make contacts W7 of the up preference relay W between the bus L1 and the break contacts 12CR2. n

The high call reversal circuit 30 `has associated therewith a row of contact segments k2 through 1611 which are successively engaged by the brush kk as the elevator car A moves. The contact segments are so located relative to the circuit 30 that each contact segment is placed below all break contacts of the high call reversal circuit which require travel of the elevator car A above such contact segment. Thus, the contact segment k9 is connected to the high call reversal circuit between the contacts 9UR2 and 9CR2. The contact segment k8v is connected between the contacts SUR? and 8CR2. The location of the remaining contact segments similarly may be ascertained by reference to Fig. 3. The brush kk is permanently connected to the bus L2 and engages and leaves each of the contact segments during up car travel in advance of the associated floor.

By inspection of the circuit 30, it will be observed that as long as a call is registered requiring travel of the elevator car to a floor above the position of the elevator car A or as long as the elevator car A is conditioned for down travel (contacts W7 are open) the high call reversal relay HC cannot be energized through the high call reversal circuit.

In certain cases it is desirable to prevent registered calls from affecting the high call reversal circuit 30. For example, it may be desirable under some conditions to prevent registered up and down floor calls for certain floors from affecting the operation of the high call reversal relay HC. To this end, make contacts of the special service relay HP are provided for the purpose of shunting the break contacts of the up oor call registering relays for the eighth through the eleventh floors and the break contacts of the down oor call registering relays for the ninth through the twelfth oors. When the relay HP is energized, the contacts HP2 through HPS close to shunt respectively the contacts SURZ and 9DR2, 9UR2 and 10DR2, IOURZ and 11DR2, and llURZ and 12DR2.

The high zone relay HZ is energized when the elevator car A is positioned above the seventh floor. To this end, a brush mm engages a contact segment m as long as thc elevator car A is above the seventh oor to establish the following circuit:

L1, m, mm, HZ, L2

The high zone quota relay QH indicates the presence of a predetermined Service demand for the ninth through the twelfth floors. As is shown in Fig. 3, the relay QH preferably is energized in accordance with the number of registered up and down floor calls for the ninth through the twelfth floors. The energization of this relay is dependent on the condition of a parallel circuit having seven parallelarms. Each arm contains a suitable resistor and a set of make contacts of a separate one of the floor call registering relays for the ninth through the twelfth floors. The resistors are so proportioned that a predetermined numbery of oor calls must be registered before the relay QH will pick up. For example, it will be assumed that at least two floor calls must be registered to provide suicient currentfor the relay QH to pick up and that4 the relay QH is dropped out when less than two floor calls are registered.

The low zone quota relay QL indicates the presence of a predetermined service demand for the second through the eighth floors. As is shown in Fig. 3, the relay QL preferably is energized in'accordance with the number cf registered downfloor calls for the second through the eighth floors. The energization of the relay QH is dependent on the condition of a parallel circuit having seven parallel arms. Each arm contains a suitable resistor and a set of make contacts of a separate one of the down floor call registering relays for the second through the eighth floors. The resistors are so proportioned that a predetermined number of down 4floor calls must be registered before the relay QL will pick up. For example, it will be assumed that at least three down floor calls must be registered to provide suflicient current for the relay QL to pick up and that this relay will be dropped out when less than three down floor calls for the second through the eighth floors yare registered.

Operation of the relays QH and QL is employed under certain conditions to effect specialized service by the entire bank of elevator cars. Such service is provided by the special service relays HP and BPP, which are initially energized through the break contacts QH and the make contacts QL1. Thus, under the assumed conditions when ne or no iloor calls are registered in the high zone (oors nine through twelve), and when three or more down oor calls are registered in the low zone (floors two HZ or BHZ, respectively, ,mentioned Pickup of either or both of these relays is through eight), the relays HP and BHP will be picked up.

Pickup of the relay HP is accompanied by closure of the make contacts HP1 partially to prepare a holding circuit for the relays HP and BHP. if, while the relays HP and BHP are picked up, either or both of the elevator cars A and B are in the high zone, either or both of the relays will be picked up, as aforeaccompanied by closure of either or both of their associated make contacts HZ?L and BHZl, respectively, to complete the holding circuit for the relays HP and BHP. It will be seen, therefore, that if the relays HP and BHP are picked up and there is an elevator car in the high zone, these relays will remain picked up although the low zone quota relay QL subsequently drops out (less than three down Hoor calls are registered in the low zone), as long as the high zone quota relay QH remains dropped out (less than two floor calls are registered in the high zone). Conversely, if the relay QL is dropped out, the relays HP and BHP will also be dropped out if there is no elevator car in the high zone regardless of the number of floor calls registered for the high zone.

Operation In order to assure a full understanding of the invention, certain typical operations of the elevator system now will be considered. First, it will be assumed that the elevator cars A and B are positioned at the lower terminal -tloor and that a passenger enters the elevator car A at the lower terminal iioor for the purpose of proceeding to the eleventh floor.

The doors of the elevator cars may be of the manuallyopened spring-closed type or may be of conventional power-operated design. Upon entering the elevator car A, the passenger presses the car call push button 11C (Fig. 2) to energize the associated car call registering relay HCR. This relay closes its make contacts 11CR1 to establish a holding circuit around the push button. The relay also opens its break contacts lllCRZ (Fig. 3) without immediately eecting system operation, since the brush kk is not in engagement with a contact segment when the elevator car A is positioned at the first floor. The high call reversal relay HC is, therefore, dropped out. inasmuch as the elevator car A is at the lower terminal Hoor, it will be understood that the up preference relay W (Fig. l) is energized and picked up.

lt will be assumed also that the elevator car A has remained at the lower terminal oor for a time sutlicient to result in closure of the break contacts 70T1. ConsequentIy, upon closure of the doors, the door relay DR closes its make contacts Dld to complete the following circuit:

L1, 70T1, Wl, F1, 21, U, M, DRL L2 Upon energization, the up switch U closes its make contacts U1 to release the elevator brake. Contacts U2 and U3 close to energize the generator eld winding 17F with proper polarity for up travel of the elevator car. Contacts U4 close to complete the following energizing circuit for the speed relay V:

L1, U4, 19, El, V, L2

The speed relay closes its make contact Vl to shunt the resistor R1 and thereby conditions the elevator car for full speed operation.

Continuing with the operation of the up switch U, the energized up switch closes its make contacts U5 to establish a holding circuit around the contacts 70T1 and W1.

The elevator car A now accelerates in the up direction for the purpose of carrying the passenger to the eleventh iloor.

It will be recalled that the running relay M also was energized. As a result of its energization, the running relay closes its make contacts M1 to prepare the relays G, E, and F for subsequent energization. The make contacts M2 close to maintain the energization of the up preference relay despite subsequent opening of the break contacts HCZ. Make contacts M3 close to energize the non-interference relay '7tlT. The non-interference relay opens its break contacts MTL but such opening has no immediate effect on the operation of the system.

Referring to Fig. 2, the running relay M opens its break contacts M4 and M5. Such contact operations have no immediate effect on the operation of the system.

As the elevator car approaches the eighth lloor to enter the high zone, the brush mm (Fig. 3) engages the contact segment m` to pick up the high zone relay HZ for the elevator car A in the manner heretofore described. Since the make contacts HP1 of the special service relay HP are open, however, closure of the make contacts HZl has no immediate effect on system operation.

As the car nears the eleventh floor, the brush bb (Fig. 2) engages the contact segment blt to energize the car call stopping relay T through the circuit L1, lCRl., bi1, bb, W3, T, L2

The car call stopping relay closes its make contacts T1 (Fig. l) to energize through the contacts M1 the three relays G, E and F in parallel. The relay G closes its make contacts G1 to establish a holding circuit around the contacts T1.

1t will also be noted that as the elevator car nears the eleventh oor, the brush kk (Fig. 3) engages the contact segment kll, which is positioned above the break contacts 11CR2. Consequently, the high call reversal relay HC is energized through the circuit L1, HC, W7, 12CR2, IZDRZ, 11UR2, kil, kk, L2

The relay HC closes its make contacts HC1 (Fig. l) t0 parallel the now closed contacts T1 and G1. Opening of the break contacts HCZ prepares the up preference relay W for subsequent deenergization.

The energization of the inductor slowdown and stopping relays E and F prepared these relays for subsequent operation. As the elevator car A nears the eleventh oor, the inductor slowdown relay E reaches the inductor plate UEP for the eleventh oor which completes a magnetic circuit, resulting in the opening of the normally closed contacts El. Such opening deenergizes the speed relay V. As a result of the deenergization of the speed relay V, the make contacts Vl open to introduce the resistor R1 in series with the generator eld winding l7F. The resulting decrease in the output of the generator slows the elevator car A to a landing speed.

As the elevator car A slowly approaches the eleventh door, the stopping relay F reaches the inductor plate UFP for the eleventh floor. This completes a magnetic circuit which results in opening of the normally closed contacts F1. In opening, the contacts Fl deenergize the up switch U and the running relay M.

The up switch U now opens its make contacts Ul to apply the elevator brake. Contacts U2 and U3 open to deenergize the generator field winding and the elevator car stops accurately at the eleventh oor. Opening of the make contacts Uf:- and U5 has no immediate effect on the operation of the system.

The running relay M opens its make contacts M1 to deenergize the relays G, E and F. The relay G opens its make contacts G1. Opening of the make contacts M2 results in deenergization of the up preference relay W at the eleventh floor, inasmuch as the break contacts HCZ are open, as heretofore explained. Deenergization of the up preference relay is accompanied by opening of the make contacts Wl, W3, W5 and W6 without affecting operation. Closure of the break contacts W2 completes an energizing circuit for the down preference relay X. Since the up preference relay is deenergized and the down preference relay X is energized, the elevator car A now is conditioned for down travel.

Continuing with the operation of the running relay M, the deenergized running relay opens its make contacts M3 to deenergize the non-interference relay 70T. This relay now starts to time out. Closure of the break contacts M (Fig. 2) has no immediate effect on system operation.

Referring to Fig. 2, it should be noted that as the elevator car A approached the eleventh iloor, the brush dd engaged the contact segment dll. When the running relay M drops out to close its break contacts M4, the following cancelling circuit is completed:

L1, 11CR1, lllCRN, dll, dd, W4, M4, L2

Consequently, the car call registering relay HCR is reset. As the car comes to a stop, the brush bb passes slightly above the associated contact segment 1711.

rl`he resetting of the car call registering relay 11CR opens the make contacts 11CR1. ln addition, the break contacts 11CR2 (Fig. 3) reclose without affecting system operation.

The make contacts W7 open to drop out the high call reversal relay HC. Opening of the make contacts HC1 has no immediate effect on operation. Preferably, the relay HC has a slight time delay in dropout to assure the opening of the break contacts X2 (Fig. l) in the circuit of the up preference relay W before the reclosure of the make contacts HG2.

Next it will be assumed that as the elevator car A was leaving the first floor in the preceding example a prospective passenger at the second oor registered an up floor call by operation of the up floor call push button 2U (Fig. 2). Such operation energizes the up floor call registering relay ZUR, which closes its contacts ZURI to establish a holding circuit around the push button. In addition, the registering relay opens its break contacts ZURZ and EURS (Fig. 3) in the high call reversal circuits 30 and B3@ for the elevator cars A and B, respectively. The present discussion, however, will be confined to the operation of the elevator car A. Since the registration of the car call for the eleventh floor in the elevator car A resulted in the opening of the break contacts 11CR2, opening of the contacts ZURZ in series therewith has no effect on operation.

As the elevator car A nears the second floor, the brush ee engages the contact segment e2 to establish the circuit L1, ZURl, e2, ee, W5, S, L2

The resultant energization of the floor call stopping relay S results in closure of the make contacts S1 (Fig. l) to energize the relays G, E and F. These cooperate to stop the elevator car A at the second floor by a sequence which will be clear from the preceding discussion of the stopping of the elevator car at the eleventh floor. As the elevator car stops, the engagement of the brush ff with the contacts segment f2 and the closure of the break contacts M5 completes the following cancelling circuit:

L1, 2UR1, ZURN, f2, ff, W6, M5, L2

This resets the up floor call registering relay ZUR in the manner previously described. As a result of this resetting, the relay opens its contacts 2UR1 and recloses its break contacts ZUR?. (Fig. 3). inasmuch as the contacts MCR?. remain open, the reclosure of the contacts ZURZ has no immediate effect on the system.

Next it will be assumed that a prospective passenger at the tenth floor registers a down oor call by operation of the push button 19D (Fig. 2) after the elevator car A reaches the eleventh floor. The resultant energization of the down floor call registering relay MDR closes the make contacts ltlDRl to establish a holding circuit around the push button. ln addition, the registering relay opens its break contacts ltlDRZ (Fig. 3) and its break contacts ltlDR for the elevator car B. Opening of the contacts WDRZ has no immediate effect on system operation. Closure of the make contacts 10131144 16 in the circuit of the high zone quota relay QH has no effect on operation, since, as previously mentioned, it is assumed that current must flow in at least two of the parallel resistors R1@ through R16 in order for the relay QH to pick up.

It will be assumed that the elevator car A has remained at the eleventh floor for time sufficient to permit reclosure of the break contacts 7tlT1 of the non-inten ference relay and that the doors have closed. Thus, pickup of the door relay DR results in closure of its make contacts DRl to complete the following circuit:

L1, T1, X1, F2, Z2, D, M, DRI, L2

The relay D upon energization closes its make contacts D1 to release the elevator brake. Contacts D2 and D3 close to energize the generator field with proper polarity for down travel. Contacts D4 close to complete through the limit switch 20 and the contacts E2 an energizing circuit `for the speed relay V. This relay closes its make contacts D1 to shunt the resistor R1. The elevator car A now accelerates to its full speed in the down direction.

`Closure of the make contacts D5 establish a holding circuit around the contacts 70T1 and X1. The running relay M upon energization operates its contacts in the manner previously described.

As the elevator car A nears the tenth floor, the brush gg engages the contact segment gli) (Fig. 2) to complete the following energizing circuit:

L1, 10DR1, gli), gg, X5, S, L2

As a result of its energization the floor call stopping relay S closes its make contacts to energize the relays G, E and F. The relay G closes its make contacts to establish a holding circuit around the contacts S1. The continued movement of the elevator car A brings the inductor slowdown relay adjacent the plate DEP `for the tenth floor and completes a magnetic circuit resulting in opening of the contacts E2. Such opening results in deenergization of the speed relay V and this relay opens its make contact V1 to introduce the resistor R1 in series with the generator eld winding. The decrease in energization of the field Winding slows the elevator car to a landing speed. The continued movement of the elevator car A at a slow speed brings the inductor stopping relay F adjacent the inductor plate DEP to open the contacts F2. Such opening dcenergizes the `down switch D and the running relay M. The down switch D opens its make contacts D1 to apply the elevator brake. Contacts D2 and D3 open to deenergize the generator eld winding and the elevator car stops accurately at the tenth floor. Opening of make contacts D4 and D5 has no immediate effect on the operation of the system.

During the stopping operation, the brush hh (Fig. 2) engages the contact segment 1110 to complete the following cancelling circuit:

L1, 10DR1, 10DRN, 1110, tz, X6, M5, L2

-In resetting, the relay NDR opens its holding contacts 10DR1. In addition, the relay closes its break contacts 10DR2 and 10DR3 (Fig. 3) and opens its make contacts 10DR4 without aifecting system operation.

It will be assumed that the passenger at the tenth floor enters the elevator car and operates the push button 2C (Fig. 2) to register a car call for the second floor. The resultant energization of the car call registering relay ZCR closes the holding contacts ZCRI. If sufficient time has elapsed for the non-interference relay 70T (Fig. l) to drop out, the break contacts 70'l`1 close. It the doors also are closed, an energizing circuit again is completed for the down switch D and the running relay M. These cooperate in the manner previously discussed to move the elevator car toward the second floor.

As the elevator car A nears the second floor the brush aa (Fig, 2) engages the contact segment a2 to complete all uergizing circuit `for the car call stopping cussion will be confined to the elevator car A.

relay T. This relay closes its make contacts T1 to energize the relays G, E and F through the contacts M1. The energized relays E and F cooperate in the manner previously described to stop the elevator car A at the second floor. As the elevator car stops, the brush cc engages the contact segment c2 to complete the following cancelling circuit:

L1, 2cm, zcRN, c2, ce, X4, M4, Lz

ln resetting, the relay ZCR opens its holding contacts L1, g1, gg, XS, S, L2

The oor call stopping relay S initiates a stopping operation of the elevator car at the first floor in the manner discussed above for the tenth floor.

As it reaches the lower termin l oor, the elevator car A opens the limit switch 24 (Fig. l) to deenergize the down preference relay. This relay closes its break contacts X2 to complete an energizing circuit through the now closed contacts HC2 for the up preference relay W as the elevator car stops -at the lower terminal floor. The deenergization of the down preference relay X and the energization of the up preference relay W condition the elevator car A for up travel.

It now will be assumed that the elevator cars A and B are both positioned at the lower terminal floor when down floor calls for elevator service are registered for the second, third, seventh and twelfth oors. Such registration results in opening of the break contacts 3DR2, 7DR2, and 12DR2 (Fig. 3). The break contacts 3DR3, 7DR3 and 12DR3 in the high call reversal circuit for the elevator car B also are opened, but the present dis- In addition, the make contacts 2DR4, 3DR4 and 7DR4 close to energize the low zone quota relay QL. It is assumed in this example that the resistors R3 through R9 are so dimensioned that currents flowing through at least three resistors are required to energize the low zone quota relay QL sufliciently to pick up the relay. Make contacts 12DR4 also close, but it is assumed that the resistors R10 through R16 are so dimensioned that currents owing through at least two resistors are required to energize the high zone quota relay QH sufficiently to pick up the relay QH.

The registration of the above-named Hoor calls indicates the presence of a substantially high demand for down service from the oors in the low zone and the presence of a low demand for down service from the oors in the high zone. Inasmuch as travel of the elevator car A to the twelfth floor to answer the single calll for down service from the high zone requires substantial time, it follows that the answering of this single call in the high zone would delay appreciably down service for the floors for which the down floor calls have been registered in the low zone. For this reason, the over-al1 trac handling of the bank of elevator cars may be improved if the single call in the high zone is penalized when a large demand for down service exists in the low zone.

When the low zone quota relay QL is energized suiciently to pick up, it closes its make contacts QL1 to establish the following energizing circuit for the special service relay HP:

L1, QL1, HP, QHl, L2 By inspection of Fig. 3 it will be observed that a similar energizing circuit is established for the special service relay BHP for the elevator car B.

Pickup of the relay HP results in closure of its make contacts HP1 partially to establish a holding circuit for the special service relays. Pickup of the relay HP also is accompanied by closure of its make contacts HP2, HPS, HP4 and HPS. Closure of the contacts HP2, HP3 and HP4 has no effect on operation, since under the assumed conditions the break contacts which they shunt are closed. Closure of the contacts HPS, however, shunts the now open contacts 12DR2. It will be observed that as long as the contacts HPS remain closed the open contacts 12DR2 cannot effect operation of the high call reversal relay HC.

The elevator car A in response to the registration of the down floor call from the seventh oor proceeds towards such floor in the up direction, bypassing the down oor calls for the second and third oors, inasmuch as the make contacts XS (Fig. 2) are open, as will be understood from the previous discussion. As the car approaches the seventh floor, the brush kk engages the contact segment k7 to complete an energizing circuit for the high call reversal relay HC. This circuit may be traced as follows:

L1, HC, W7, 12CR2, HPS, 11CR2, HP4 or 11DR2 and 10UR2, 10CR2, HPS or 10DR2 and 9UR2, 9CR2, HP2 or 9DR2 and 8UR2, 8CR2, SDRZ, 7UR2, k7, kk, L2

The energization of the high call reversal relay results in closure of the make contacts HC1 (Fig. l) to establish with the closed contacts M1 an energizing circuit for the relays G, E and F. These operate in the manner previously discussed to stop the elevator car A at the seventh oor. It should be noted that the elevator car while traveling up is stopped at the seventh oor in response to a down oor call. This down oorcall is the farthest call in the low zone in the direction of travel of the elevator car.

The relay HC also opens its make contacts HCZ. Inasmuch as the make contacts M2 open as the car stops, it follows that the up preference relay W is deenergized at the seventh oor. Deenergization of the up preference relay isaccompanied by closure of the break contacts W2 to complete an energizing circuit for the down preference relay X. Cancellation of the down oor call for the seventh door results in the opening of the make contacts 7DR4 (Fig. 3) in the circuit of the low zone quota relay QL, causing this relay to drop out. Opening of the make contacts QL1 results in deenergization of the special service relays HP and BHP. Dropout of the relay HP, accompanied by the opening of the break contacts HPS, has no elect on system operation, however, since the make contacts W7 now are open, inasmuch as the up preference relay W is dropped out. Since the up preference relay is deenergized and the down preference relay X is energized, the elevator car A now is conditioned for down travel. The car subsequently proceeds to the third door and then to the second oor to answer the previously registered down floor calls for those oors. The operation of the system in answering such calls will be understood from the foregoing discussion.

It will be noted that the down floor call which was previously registered for the twelfth door has thus far remained unanswered. After return of the elevator car A to the rst floor, however, the car may answer the twelfth floor call since the elevator system no longer is conditioned for specialized service operation, as is discussed above. Thus, it will be observed that down service in response to the relatively heavy trac demand from the low zone has been expedited, whereas the single call from the twelfth door in the high zone has been penalized. In actual practice, it is unlikely that the prospective passenger at the twelfth oor will vhave to 19 wait an undue length of time, inasmuch as both the elevator cars A and B are available to respond to the heavy vdernand for down service from the low zone and inasmuch as such demand from only the low zone is unlikely to occur for more than a relatively short period of time.

VIn the foregoing example, had there been no call in the high zone, the operation of the system nevertheless would have been the same, since the low zone quota relay QL Would have picked up upon the registration of the three down floor calls from the low zone while the high zone quota relay QH would have remained dropped out. Likewise, had a single up floor call been registered from the high zone rather than the down floor call from the twelfth floor, the elevator system ywould have been transferred to a vspecialized service operation. The foregoing will be apparent from inspection of Fig. 3, wherein it will be observed that the make contacts HP2 through HPS shunt contacts of both the up and the down floor call registering relays for the high zone in the circuit of the high call reversal relay HC.

It also will be observed, under the assumed conditions, that if two or more floor calls (up and/ or down) are registered from the high zone, the resulting pickup of the high zone quota relay QH will prevent specialized service operation of the system regardless of the number of down fioory calls registered from the low zone. This follows from the fact that pickup of the relay QH results in opening of its break contacts QH1 which prevents energization of the special service relays HP and BHP. Thus, in the present system the elevator cars may ignore, during specialized service operation, a maximum of one registered floor call in the high zone; and when this number is eX- ceeded, the system provides normal high call reversal service for all of the floors. In addition, it will be noted that during specialized service operation, both of the elevator cars A and B are permitted to answer car calls for all of the floors, since operation of the special service relays does not affect the contacts of the car call registering relays ICR through IZCR. Furthermore, both of the cars may respond to up floor calls from floors in the low zone during specialized service operation. It is likely, however, that there will be relatively few car calls for floors other than the first floor and relatively few up oor calls during periods of heavy down traiiic. If there is a car call above a floor for which a floor call (up or down) is registered in the high zone while the system is on specialized service operation, the car will answer such floor call by operation of the floor call stopping relay S (Fig. 2), as will be apparent from the preceding discussion. If, however, there is a car call for a high zone lioor which is below a floor for which a floor call in the high Zone is registered while the system is on specialized service operation, the elevator car will reverse its direction of travel at the iioor for which the car call is registered. This will be apparent when it is recalled that the high zone oor call registering relay contacts in the high call reversal circuits 30 and B30 (Fig. 3) ofthe elevator cars A and B are then shunted by contacts of the special service relays HP and BHP, respectively.

For theV next example it will be assumed that the system is on specialized service operation (relays HP and BHP are picked up) and that elevator car A is in the high zone either because it was there when the system was transferred to specialized service operation or that it proceeded to the high zone from the low zone in response to a car call for the high zone after the transfer to specialized service operation. As heretofore explained, when the car A is in the high zone, the high zone relay HZ (Fig. 3) is picked up. Closure of the make contacts HZl completes with the closed contacts HP1 a holding circuit for the special service relays HP and BHP through the closed contacts QH1. It will be assumed further that ywhile this holding circuit is complete (the car A remains in the high zone) the low zone quota relay QL drops out. Such dropout may occur, for example, if the elevator car B answers a suicient number of down floor calls in the low zone so that less than three such calls remain. it will be noted in addition that as long as there are less than two floor calls in the high zone, the high zone quota relay QH remains dropped out to maintain its break contacts QH1 closed. Thus, although the low zone quota relay QL has dropped out, the special service relays HP and BHP remain picked up to maintain their make contacts HP2. through HPS and BHPZ through BHP5, respectively, in closed condition. Such operation prevents the elevator car B from serving the high zone in response to a registered floor call therefrom until the elevator car A reenters the low zone. When the car A reenters the low zone, the high zone relay HZ is deenergized to open the contacts H21 and thus to open the holding circuit for the relays HP and BHP. If, when the car A reenters the low zone, the low zone quota relay QL is still dropped out, normal elevator service for all of the floors will be restored. If, however, before the elevator car A reenters the low zone the relay QL is reenergized (due to the reregistration of three or more low zone down floor calls), specialized service will be maintained, as long as less than two high zone floor calls are registered it will be observed that such operation of the relay HZ prevents hunting of the system from specialized service operation to normal operation if less than three down fioor calls are registered in the low zone for only relatively short periods of time while the elevator car A is positioned in the high zone (and similarly for the elevator car B).

Although the invention has been described with reference to certain specific embodiments thereof, numerous modifications falling within the spirit and scope of the invention are possible.

I claim as my invention:

1. ln an elevator system, a structure having landings to be served by an elevator car, said landings comprising first and second groups, an elevator car, means mounting the elevator car for movement relative to the structure to serve the landings, call means for registering calls for elevator service for each of a plurality of the landings in each of said groups, control means for operating the elevator car in a first direction and in a second direction opposite to said first direction and for stopping the elevator car at each landing in said first and second groups for which a call for elevator service is registered to provide a first mode of service for said landings, modifying means responsive to the registration by said call means of greater than a first predetermined number of calls for the first group of said landings for conditioning the elevator car. to provide a second mode of service for said landings, and means responsive to the registration by said call means of greater than a second predetermined number of calls for the second group of said landings for preventing the elevator car from providing said second mode of service although greater than said first predetermined number of calls is registered by said call means for the first group of said landings, said second predetermined number being greater than zero.

2. In an elevator system, a structure having landings to be served by an elevator car, said landings comprising first and second groups, an elevator car, means mounting the elevator car for movement relative to the structure to serve the landings, landing call means operable from each of a plurality of the landings in each of said groups for registering calls for elevator service in a first direction of travel from said landings, control means for operating the elevator car for travel in said first direction and in a second direction opposite to said first direction and for stopping the elevator car at each landing in said first and second groups for which a call for service is registered by said landing call means, modifying means responsive to the registration by said landing call means of greater than a first predetermined number of calls for said first group of landings for conditioning the elevator car to serve only said first group of landings although a call is registered by said landing call means for said second group of landings, and means responsive to the registration by said landing call means of greater than a second predetermined number of calls for the second group of said landings for preventing the elevator carfrom serving only said first group of landings although greater than said first predetermined number of calls is registered by said landing call means forA said first group of landings, said second predetermined number being greater than zero.

3. In an elevator system, a stiucture having landings to be served by an elevator car, said landings comprising first and second groups, an elevator car, means mounting the elevator car for movement relative to the structure to serve the landings, landing first call means operable from each of a plurality of the landings in each of said groups for registering calls for elevator service in a first direction of travel from said landings, landing second call means operable from each of a plurality of the landings in each of said groups for registering calls for elevator service in a second direction of travel opposite to said first direction from said landings, control means for operating the elevator car for travel in said first and second directions and for stopping the elevator car at each landing in said first and second groups for which a call for service is registered by said landing first or second call means, modifying means responsive to the registration by said landing first call means of greater than a first predetermined number of calls for said first group of landings for conditioning the elevator car to serve only said first group of landings although a call is registered by said landing first or second call means for said second group of landings, and means responsive to the registration by said landing first and second call means of greater than a second predetermined number of calls for said second group of landings for preventing the elevator car from serving only said rst group of landings although greater than said first predetermined number of' calls is registered by said landing first call means for said first group of landings, said second predetermined number being greater than zero.

4. In an elevator system, a structure having landings to be served by an elevator car, said landings comprising first and second groups, an elevator car, means mounting the elevator car for movement relative to the structure to serve the landings, landing first call means operable from each of a plurality of the landings in each of said groups for registering calls for elevator service in a first direction of travel from said landings, landing second call means operable from each of a plurality of the landings in each of said groups for registering calls for elevator service in a second direction of travel opposite to said first direction from said landings, car call means for registering calls for elevator service for landings desired by passengers entering the elevator car, control means for operating the elevator car for travel in said first and second directionsand for stopping the elevator car at each landing in said first and second groups for which a call for service is registered by said landing first or second call means or by said car call means, modifying means responsive to the registration by said landing first call means of greater than a first predetermined number of calls for said first group of landings for conditioning the elevator car to` serve only said first group of landings although a call is registered by said landing first or second call means for said second group of landings provided that no call is registered by said car call means for a landing in said second group, and means responsive to the registration by said landing rst and second call means of greater than a second predetermined number of calls for said second group of landings for preventing the elevator car from serving only said first group of landings although greater than said first predetermined number of calls is registered by said landing first call 22 means for said first group of landings, said second predetermined number being greater than zero.

5. In an elevator system, a structure having a plurality of landings, a bank of elevator cars, means mounting the elevator cars for movement relative to the structure to serve the landings, motive means for moving the elevator cars relative to the structure, landing call means operable from each of the landings for registering calls for elevator service for the landings, and control means operable in cooperation with the motive means and the landing call means for moving and stopping the elevator cars to answer calls for elevator service, said control means including means responsive to a predetermined traffic condition for conditioning all of the elevator cars of said bank to serve the same part only of said landings although a call for elevator service is registered by said landing call means for the remaining part of said landings.

6. ln an elevator system for a structure having a plurality of landings, a bank of elevator cars, means mounting the elevator cars for movement in two directions relative to the structure to serve said landings, motive means for moving the elevator cars relative to the structure, and control means for controlling the movement of the elevator cars by the motive means and the stopping of the elevator cars at predetermined landings, said control means comprising landing call means operable from each of the landings for registering calls for elevator service in a first of said two directions of travel from said landings, said control means including means for controlling the movement of each of the elevator cars for travel in said two directions and for stopping each of the elevator cars at each of the landings approached by the respective elevator cars for which a call is registered by said landing call means which may be answered by the approaching elevator car without a change in the direction of travel of the approaching elevator car, and means responsive to a predetermined trafiic condition for conditioning all of the elevator cars of said bank to serve the same part only of said landings although a call for elevator service is registered by said landing call means for the remaining part of said landings and for causing each of the elevator cars when traveling in the Isecond of said two directions to stop and to reverse its direction of travel at the farthest landing in said same part for which a call is -registered by said landing call means which may be answered by the last-named elevator car.

7. In an elevator system for a structure having a plurality of landings, a bank of elevator cars, means mounting the elevator cars for movement in two directions relative to the structure to serve said landings, motive means for moving the elevator cars relative to the structure, and control means for controlling the movement of the elevator cars by the motive means and the stopping of the elevator cars at predetermined landings, said control means comprising landing first call means operable from each of the landings for registering calls for elevator service in a first of said two directions of movement from said landings and landing second call means operable from each of the landings for registering calls for elevator service in the second of said two directions of movement from said landings, said controlmmeans including means for controlling the movement of each of the elevator cars for travel in said two directions and for stopping each of the elevator cars at each of the landings approached by the respective elevator cars for which a call is registered by said landing first or second call means which may be answered by the approaching elevator car without a change in the direction of travel of the approaching elevator car, and means responsive to a predetermined trafiic condition for conditioning all of the elevator cars of said bank to serve the same part only of said landings although a call for elevator service is registered by said landing first or second call means for the remaining part of said landings and for causing each of the elevator cars when traveling in the second direction to stop and to reverse its direction of travel at the farthest landing in said same part for which a call is registered by said landing first call means which may be answered by the last-named elevator car provided that no call is registered by said landing second call means for such farthest landing requiring further travel of the last-named elevator car from such farthest landing in said second direction.

8. In an elevator system for a structure having a plurality of landings, a bank of elevator cars, means mounting the elevator cars for movement in two directions relative to the structure to serve said landings, motive means for moving the elevator cars relative to the structure, and control means for controlling the movement of the elevator cars by the motive means and the stopping of the elevator cars at predetermined landings, said control means comprising first call registering means operable from each of the landings for registering calls for elevator service in a first of said two directions of movement from said landings, second call registering means operable from each of the landings for registering calls for elevator service in the second of said two directions of movement from said landings, third call registering means for each of the elevator cars operable for registering a call for each of the landings desired for the load within the associated elevator car, said control means including means for controlling movement of each of the elevator cars for travel in said two directions and for stopping each of the elevator cars at any of the oors approached by such elevator car for which a call for service is registered by said first, second or third call registering means which may be served by movement of such elevator car in the direction of such approach, and means responsive to a predetermined traffic demand for conditioning all of the elevator cars of said bank to serve the same part only of said landings although a call for elevator service is registered by said first or second call registering means for the remaining part of said landings and for causing each of the elevator cars when traveling in said second direction to stop and to reverse its direction of travel at the farthest landing in said same part for which a call is registered by the first call registering means which may be answered by the last-named elevator car or the third call registering means for the last-named elevator car provided that no call is registered by the second call registering means for such farthest landing and no call is registered by the third call registering means for said remaining part of said landings requiring further travel of the last-named elevator car from such farthest landing in said second direction.

9. In an elevator system, a structure having a plurality of landings, a plurality of elevator cars, means mounting the elevator cars for movement relative to the structure to serve the landings, motive means for moving the elevator cars relative to the structure, landing call means operable from each of the landings for registering calls for elevator service for the landings, control means operable in cooperation with the motive means and the landing call means for moving and stopping the elevator cars to answer calls for elevator service, modifying means responsive to the registration by said landing call means of greater than a first predetermined number of calls for elevator service for a predetermined part of said landings for conditioning all of said elevator cars to serve only said predetermined part of said landings although a call for elevator service is registered by said landing call means for the remaining part of said landings, and means responsive to the registration by said landing call means of greater than a second predetermined number of calls for elevator service for said remaining part of said landings for preventing said elevator cars from serving only said predetermined part of said landings although greater than said first predetermined number of calls is registered by said landing call means for said predetermined part of said landings, said second predetermined number being greater than zero.

l0. An elevator system including a structure having landings, said landings comprising first and second groups, a plurality of elevator cars, means mounting the elevator cars for movement relative to the structure to serve the landings, landing call means operable from each of said landings for registering calls for elevator service in a first direction of travel from said landings, control means for operating each of the elevator cars for travel in said first direction and in a second direction opposite to said first direction and for stopping each of the elevator cars at each of the landings approached by the respective elevator cars for which a call is registered by said landing call means which may be answered by the approaching elevator car without a change in the direction of travel of the approaching elevator car, modifying means responsive to the registration by said landing call means of greater than a first predetermined number of calls for said first group of landings for conditioning all of said elevator cars to serve only said first group of landings and for causing each of the elevator cars while traveling in the second direction to stop and to reverse its direction of travel at the farthest landing in said first group reached by the last-named elevator car for which a landing call is registered by said landing call means which may be answered by the last-named elevator car although a call is registered by said landing call means for said second group of landings, and means responsive to the registration by said landing calls means of greater than a second predetermined number of calls for the second group of said landings for preventing said elevator oars from serving only said first group of landings although greater than said first predetermined number of calls is registered by said landing call means for said first group of landings, said second predetermined number being greater than zero.

l1. An elevator system including a structure having landings, said landings comprising first and second groups, a plurality of elevator cars, means mounting the elevator'- cars for movement in two directions relative to the structure to serve the landings, landing first call means oper-y able from each of the landings for registering calls for elevator service in a first of said two directions of movement from said landings, landing second call means operable from each of the landings for registering calls for elevator service in the second of said two directions of movement from said landings, control means for operating each of the elevator cars for travel in said two directions and for stopping each of the elevator cars at each of the landingsapproached by the respective elevator cars for which a call is registered by said landing first or second call means which may be answered by the approaching elevator car without a change in the direction of travel of the approaching elevator car, modifying means responsive to the registration by said landing first call means of greater than a first predetermined number of calls for said rst group of landings for conditioning all of said elevator cars to serve only said first group of landings although a call is registered by said landing first or second call means for said second group of landings and for causing each of the elevator cars while traveling in the second direction to stop and to reverse its direction of travel at the farthest landing in said first group reached by the last-named elevator car for which a call is registered by said landing first call means which may be answered by the last-named elevator car provided that no call is registered by said landing second call means for such farthest landing whichv can be answered only by continued movement of the last-named elevator car from such farthest landing in said second direction, and means responsive to the registration by said landing first and second call means of greater than a second predetermined `able from each of number of calls for said second group of landings for preventing said elevator cars from serving only said first group of landings although greater than said first predetermined number of calls is registered by said landing rst call means for said first group of landings, said second predetermined number being greater than Zero.

12. An elevator system including a structure having landings, said landings comprising first and second groups, a plurality of elevator cars, means mounting the elevator` cars for movement in two directions relative to the structure to serve the landings, landing rst call means operable from each of the landings for registering calls for elevator service in a first of said two directions of movement from said landings, landing second call means operthe landings for registering calls for elevator service in the second of said two directions of movement from said landings, car call means for each of lthe elevator cars operable for registering a call for each of the landings desired for the load within the associated elevator car, control means for operating each of the ele- 'vator cars for travel in said two directions and for stopping each of the elevator cars at each of the landings approached by the respective elevator cars for which a call for service is registered by said landing first or second call means or by said car call means which may be answered by the approaching elevator car without a change in the direction of travel of the approaching elevator car, modifying means responsive to the registration by said landing first call means of greater than a first predetermined number of calls for said first group of landings for conditioning all of said elevator cars to serve only said first group of landings although a call is registered by said landing first or second call means for said second group of landings and for causing each of the elevator cars while traveling in the second direction to stop and to reverse `its direction of travel at the farthest landing in said first group reached by the last-named elevator car for which a call is registered by said landing first call means or by said car call means which may be answered by the lastnamed elevator car provided that no call is registered by said landing second call means for such farthest landing and no call is registered by said car call means for said second group of landings requiring further travel of the last-named elevator car from such farthest landing in said second direction, and means responsive to the registration by said landing first and second call means of greater than a second predetermined number of calls for the second group of said landings for preventing said elevator cars from serving only said first group of landings although greater than 'said first predetermined number of calls is registered by said landing first call means for said first group of landings, said -second predetermined number being greater than zero.

13. In an elevator system, a structure having a plurality of landings, a bank of elevator cars, means mounting the elevator cars for movement relative to the structure to serve the landings, motive means for moving the elevator cars relative to the structure, landing call means operable from each of the landings for registering calls for elevator car service for the landings, and control means operable in cooperation with the motive means and the landing call means for moving and stopping the elevator cars to answer calls for elevator service, said control means including means responsive to a first predetermined traffic condition for conditioning all of the elevator cars of said bank to serve the same part only of said landings although a call for elevator service is registered by said landing call means for the remaining part of said landings, and means for preventing any of said elevator cars from serving said remaining part of said landings upon the termination of said first predetermined traffic condition except upon the occurrence of a second predetermined traffic condition.

14. In an elevator system for a structure having a plurality of landings, a bank of elevator cars, means mounting the elevator cars for movement in two directions relative to the structure to serve said landings, motive means for moving the elevator cars relative to the structure, and control means for controlling the movement of the elevator cars by the motive means and the stopping of the elevator cars at predetermined landings, said control means comprising landing call means operable from each of the landings for registering calls for elevator service in a rst of said two directions of travel from said landings, said control means including means for controlling the movement of each of the elevator cars for travel in said two directions and for stopping each of the elevator cars at each of the landings approached by the respective elevator cars for which a call is registered by said landing call means which may be answered by the approaching elevator car Without a change in the direction of travel of the approaching elevator car, means responsive to a first predetermined traffic condition for conditioning all of the elevator cars of said bank to serve the same part only of said landings although a call for elevator service is registered by said landing call means for the remaining part of said landings and for causing each of the elevator cars when traveling in the second of said two directions to stop and to reverse its direction of travel at the farthest landing in said same part for which a call is registered by said landing call means which may be answered by the last-named elevator car, and means for preventing any of said elevator cars from serving said remaining part of said landings upon the termination of said first predetermined traflic condition except upon the occurrence of a second predetermined trafic condition.

15. In an elevator system for a structure having a plurality of landings, a bank of elevator cars, means mounting the elevator cars for movement in two directions relative to the structure to serve said landings, mo- Itive means for moving the elevator cars relative to the structure, and control means for controlling the movement of the elevator cars by the motive means and the stopping of the elevator cars at predetermined landings, said control means comprising landing first call means operable from each of the landings for registering calls for elevator service in a first of said two directions of movement from said landings and landing second call means operable from each of the landings for registering calls for elevator service in the second of said two directions of movement from said landings, said control means including means for controlling the movement of each of the elevator cars for travel in said two directions and for stopping each of the elevator cars at each of the landings approached by the respective elevator cars for which a call is registered by said landing first or second call means which may be answered by the approaching elevator car without a change in the direction of travel of the approaching elevator car, means responsive to a first predetermined trafiic condition for conditioning all of the elevator cars of said bank to serve the same part only of said landings although a call for elevator service is registered by said landing first or second call means for the remaining part of said landings and for causing each of the elevator cars when traveling in the second direction to stop and to reverse its direction of travel at the farthest landing in said same part for which a call is registered by said landing first call means which may be answered by the last-named elevator car provided that no call is registered by said landing second call means for such farthest landing requiring further travel of the last-named elevator car from such farthest landing in said second direction, and means for preventing any of said elevator cars from serving said remaining part of said landings upon the termination of said first predetermined traffic condition except upon the occurrence of a second predetermined traflic condition.

16. In an elevator system for a structure having a plurality of landings, a bank of elevator cars, means mounting the elevator cars for movement in two directions relative to the structure to serve said landings, motive means for moving the elevator cars relative to the structure, and control means for controlling the movement of the elevator cars by the motive means and the stopping of the elevator cars at predetermined landings, said control means comprising first call registering means operable from each of the landings for registering calls for elevator service in a first of said two directions of movement from said landings, second call registering means operable from each of the landings for registering calls for elevator service in the second of said two directions of movement from said landings, third call registering means for each of the elevator cars operable for registering a call for each of the landings desired for the load within the associated elevator car, said control means including means for controlling movement of each of the elevator cars for travel in said two directions and for stopping each of the elevator cars at any of the floors approached by such elevator car for which a call for service is registered by said first, second or third call registering means which may be served by movement of such elevator car in the direction of such approach, means responsive to a first predetermined service demand for conditioning all of the elevator cars of said bank to serve the same part only of said landings although a call for elevator service is registered by said first or second call registering means for the remaining part of said landings and for causing each of the elevator cars when traveling in said second direction to stop and to reverse its direction of travel at the farthest landing in said same part for which a call is registered by the first call registering means which may be answered by the last-named elevator car and the third call registering means for the lastnamed elevator' car provided that no call is registered by the second call registering means for such farthest landing and no call is registered by the third call registering means for said remaining part of said landings requiring further travel of the last-named elevator car from such farthest landing in second direction, and means for preventing any of said elevator cars from serving said remaining part of said landings upon the termination of said first predetermined service demand except upon the occurrence of a second predetermined service demand.

17. In an elevator system, a structure having a plurality of landings, a plurality of elevator cars, means mounting the elevator cars for movement relative to the structure to serve the landings, motive means for moving the elevator cars relative to the structure, landing call means operable from each of the landings for registering calls for elevator service for the landings, control means operable in cooperation with the motive means and the landing call means for moving and stopping the elevator cars to answer calls for elevator service, modifying means responsive to the registration by said landing call means of greater than a first predetermined number of calls for a predetermined part of said landings for conditioning all of said elevator cars to serve only said predetermined part of said landings although a call is registered by said landing call means for the remaining part of said landings, means for preventing said elevator cars from serving said remaining part of said landings upon the termination of the registration by said landing call means of said first predetermined number of calls for said predetermined part of said landings except upon the occurrence of a predetermined traffic condition, and means responsive to the registration by said landing call means of greater than a second predetermined number of calls for said remaining part of said landings for initially preventing said elevator cars from serving only said predetermined part of said landings although greater than said first predetermined number of calls is registered by said landing call means for said predetermined part of said landings, said second predetermined number being greater than zero.

18. An elevator system including a structure having landings, said landings comprising first and second groups, a plurality of elevator cars, means mounting the elevator cars for movement relative to the structure to serve the landings, landing call means operable from each of said landings for registering calls for elevator service in a first direction of travel from said landings, control means for operating each of the elevator cars for travel in said first direction and in a second direction opposite to said first direction and for stopping each of the elevator cars at each of the landings approached by the respective elevator cars for which a call is registered by said landing call means which may be answered by the approaching elevator car without a change in the direction of travel of the approaching elevator car, modifying means responsive to the registration by said landing call means of greater than a first predetermined number of calls for said first group of landings for conditioning all of said elevator cars to serve only said lirst group of landings and for causing each of the elevator cars while traveling in the second direction to stop and to reverse its direction of travel at the farthest landing in said first group reached by the last-named elevator car for which a landing call is registered by said landing call means which may be answered by the last-named elevator car although a call is registered by said landing call means for said second group of landings, means for preventing said elevator cars from serving said second group of landings upon the termination of the registration by said landing call means of said first predetermined number of calls for said first group of landings except upon the occurrence of a predetermined traffic condition, and means responsive to the registration by said landing call means of greater than a second predetermined number of calls for the second group of said landings for initially preventing said elevator cars from serving only said first group of landings although greater than said first predetermined number of calls is registered by said landing call means for said first group of landings, said second predetermined number being greater than Zero.

19. An elevator system including a structure having landings, said landings comprising first and second groups, a plurality of elevator cars, means mounting the elevator cars for movement in two directions relative to the structure to serve the landings, landing first call means operable from each of the landings for registering calls for elevator service in a first of said two directions of movement from said landings, landing second call means operable from each of the landings for registering calls for elevator service in the second of said two directions of movement from said landings, control means for operating each of the elevator cars for travel in said two directions and for stopping each of the elevator cars at each of the landings approached by the respective elevator cars for which a call is registered by said landing first or second call means which may be answered by the approaching elevator car without a change in the direction of travel of the approaching elevator car, modifying means responsive to the registration by said landing first call means of greater than a first predetermined number of calls for said first group of landings for conditioning all of said elevator cars to serve only said first group of landings although a call is registered by said landing f1rst or second call means for said second group of landings and for causing each of the elevator cars while traveling in the second direction to stop and to reverse its direction of travel at the farthest landing in said rst group reached by the last-named elevator car for which a call is registered by said landing first call means which may be answered by the last-named elevator car provided that no call is registered by said landing second call means for such farthest landing which can be answered only by continued movement of the last-named elevator car from such farthest landing in said second direction, means for preventing said modifying means from becon ing ineffective upon the termination of the registration by 

